The overall long-range objective of the project resides in a systematic description of psychophysical characteristics and of underlying physiological processes of biological sensory systems. The current emphasis is on the auditory system, but investigations of receptor processes extend to the mechanoreceptive Pacinian corpuscles, and psychophysical scaling to vibrotaction and vision. The first extension aims at testing the interrecptor similarity of receptor input-output characteristics; the second, the generality of natural obsolute units subjects appear to use in magnitude estimation and production experiments. Within the auditory system the main thrust of research planned for the coming year is directed at the mechanical and receptor processes in the cochlea of the mammalian inner ear. Recent experiments have suggested that the frequency analysis seen in basilar-membrane vibration is sharpened mechanically prior to stimulation of the hair cells. We have discovered a mechanism that could be responsible for this sharpening and plan to investigate experimentally if it actually occurs in the cochlea. We also plan to record receptor potentials from cochlear inner hair cells to find out how much signal processing seen in auditory-nerve fibers takes place prior to neural spike generation. The studies are of a basic nature but have important applications to diagnosis and therapy of auditory disorders, to neurology, and to the evaluation of environmental impact on people.